Numerous thermoplastically processable polymers which contain agrochemically active compounds and can be used in crop protection have already been disclosed (cf. DE-A 4 002 736, U.S. Pat. No. 4,743,448, U.S. Pat. No. 4,666,767 and U.S. Pat. No. 5,201,925). However, these systems have the disadvantage that it is a priori unforeseeable whether a sufficient amount of the active components is released over a sufficiently long period of time. Moreover, after the end of the treatment, polymers and active compound residues remain in the soil or on the plants where they are undesirable and have to be disposed of in a costly manner.
Furthermore, polymeric carrier materials have been disclosed which are partially or completely degraded hydrolytically, during or after their application, by enzymes and/or by microorganisms (cf. Envir. Sci. and Techn. 7 (1973), 955, Coat Plast. Chem. 42 (1980), 436-440, Proc. Int. Symp. Contr. rel. Bioact. Mat. 12 (1985), 179, J. Appl. Pol. Sci 28 (1983), 327-334, "Biomaterials", Thieme Verlag, Stuttgart-New York, 1987, pages 1-65, Chem. Soc. 1990, 127-148, Chem. Pharm. Bull. 37 (1989), 1954-1956 and Macromolecules 23 (1990), 26-31). Suitable substances for such systems are, for example, polylactic acids and copolymers thereof, polycaprolactone and also polyhydroxybutyrates and copolymers thereof. However, these polymers have hitherto either been unsuitable for an economical formulation of agrochemically active compounds, or the active compounds were not released in a satisfactory manner.
In addition, numerous other biodegradable preparations composed of carrier materials and agrochemically active compounds have been described which release the active components under the application conditions. Thus, suitable carrier substances are, for example, hydrophilic polymers based on polysaccharides, such as starch, into which water-insoluble polymers are incorporated in the form of blends, for mechanical stabilization and to regulate the release of active compounds (cf. Biomaterials 10 (1989) 400-412). However, the biological degradability of these preparations leaves a great to be desired, as does the cost of producing them (cf Study of the European Commission Directorate General XII, EUR 16 102 EN).
It is furthermore possible to use destructured hydrophilic polymers in combination with at least one water-insoluble, synthetic and thermoplastic polymer as carrier substances for active compounds (cf. EP-A 0 344 118). Likewise, it is possible to use blends based on biodegradable starch and synthetic polymers containing at least one free carboxyl group for the abovementioned purpose (cf EP-A 0 404 727). However, it is disadvantageous that in each case only the hydrophilic polymer components are biodegraded, while the other polymer components remain as undesirable residues.
Finally, it has also been disclosed that fibres based on polyhydroxyalkoxides and polysaccharides or copolymers based on tartaric acid and/or lactic acid can act as carriers and/or matrix for active compounds (cf. EP-A 0 132 299, EP-A 0 253 490, EP-A 0 126 827 and DE-A 3 936 191). However, it is unfavourable that the incorporation of the active compounds causes problems, or that the degradability or the release of the active compounds is not always unsatisfactory.